High sensitivity X-ray detector based on a 25 µm-thick ZnO film

In the field of direct-conversion flat panel X-ray detector, semiconductor with thickness of tens to hundreds microns is needed. In this paper, we demonstrate that thick ZnO semiconductor deposited by RF magnetron sputtering can be candidate for the X-ray detector. The 25 µm ZnO film was prepared by sputtering method under 200 °C and a p⁺-Si/ZnO X-ray detector based on the thick ZnO film was investigated to explore its X-ray detection properties. The detector shows nonzero short circuit current and open circuit voltage indicating the heterojunction nature of the ZnO film in contact with the p⁺-Si substrate. The detector shows linear response to the X-ray dose rate and has a high sensitivity of 128 μC∙Gy⁻¹∙cm⁻² at −20 V under 30 kV_p X-rays indicating its great potential in the flat panel X-ray detector applications. The on-off response of the detector is related to the V_O defect in the ZnO film, which can be verified from the transmission spectrum, the thermal stimulated current spectrum, and the photoluminescence spectrum.